The Molecular Cytogenetics Core provides MSKCC investigators with effective chromosome-based analysis for both human and research animal cells and provides valuable support to investigators focused on understanding chromosomal instability in cancer, documentation of cell line identity and chromosomal integrity following genetic manipulations. The Molecular Cytogenetics Core processes samples from primary cells, cell lines, or archival tissue. The Core performs chromosome analysis on research samples, using conventional cytogenetics (chromosome banding and karyotyping) and molecular cytogenetics procedures based on fluorescence in situ hybridization (FISH), including Spectral Karyotyping. Staff assist investigators in designing the most appropriate and efficient analyses for their needs and produce customized probes for specific projects. The Core has assembled a broad range of molecular cytogenetics resources, including locus-specific plasmid and BAC done stocks, and individual whole chromosome painting probes. For example, the Massague lab examined the molecular basis of the link between metastasis and chemoresistance. Cancer cells that overexpress CXCL1/2 were examined. The Core provided preparation of specific probes and performed FISH to confirm sex-mismatched mouse bone marrow engraftment (XY FISH on blood smears), and performed CXCL1/2 DNA copy analysis on tissue sections of human breast tumor and metastases (frozen, paraffin, and tissue microarray) to demonstrate copy number increase and amplification. The services and collaborative work provided by the Molecular Cytogenetics Core have supported the research of 29 investigators in the past year. During the past grant period, the work of the Core has contributed to 101 publications of researchers from 6 research programs.